Process and apparatus for liquefying and rectifying air or other gaseous mixtures



Dec. 27, 1932. H LEVlN 1,892,155

PROCESS AND APPARATUS FOR LIQUEFYING AND RECTIFYING AIR OR OTHERGA'SEOUS MIXTURES Filed July 51. 1930 Patented Dec. 27, 1932 PATENTOFFICE ISAAC H. LEVIN, OF PITTSBURGH, PENNSYLVANIA rnocnss AND nrrnnarusron monnrxme AND nno-rrrme AIR on o'rann GASEOUS mrxrnnns Applicationfled July 81, 1930,

This invention relates to improvements in the process of production ofliquid air or similar gases and of separating air or other gaseousmixtures into their constituents by TI liquefaction and rectification bythe air of two or several circuits. The aim of the invention is toutilize to the maximum the relatively inexpensive source of cold asammonia or other easily liquefiable gases.

The advantages of my invention and means for obtaining these advantageswill be clearly set forth in the description of an apparatus that can beemployed as a matter of example to carry out the invention. Theaccompany- 16 ing drawing shows schematically an apparatus in which theprocess may be practiced.

Referring to said drawing, air or other gaseous mixtures is compressedin a compressor 6 and is supplied to an interchanger 4 as through a pipe5. The air is compressed and purified in the usual manner beforereaching 5. In interchanger 4, the air is cooled b heat transfer contactwith a refrigerant sucii as ammonia or the like.

i The refrigerating system is operated, for

example, by the apparatus represented in the drawing, in which acompressor 1 is used for compressing the ammonia. The ammonia iscondensed in coil 2 and expanded in valve 80 3. The expanded ammoniaenters into interchanger 4, and comes in heat transfer contactpreferably by counter current with the air to be cooled and is thenagain compressed and the cycle is repeated.

The above refrigerating cycle is given only as a matter of example, andcan be varied in many ways, so long as the desired refrigerating effectsare produced upon the compressed air. A valve is provided at 7 to drainany moisture that is collected in the interchanger.

The air leaving the interchanger 4 may be expanded into expansion valve8, or in the expansion engines 9 and/or 10, into the interchanger 11 asthrough pipe 12. While several ex anding means are shown, expansion canta e place either through valve 8 without the use of either of theengines shown, or the expansion may take place through the enginewithout being previously expanded in the Serial 110. 472,020, and inFrance August 8, 1929.

valve. Furthermore, the work done by both engines may be combined in oneunit or but a single stage engine need be used. The expansion can thustake place in either of the units shown or in the combination of all ofthem.

In addition to passing into pipe 12 the expanded air may connect tocontainer 14, which is a collector for liquefied portions of the air orgas, as through pipe 13, and so deposit any liquefied portions that mayhave resulted from the expansion.

Another portion of air is compressed in 16 and passed into interchanger18 as through pipe 17, then into interchanger 11, and '85 u its heat incounter current to cold air in pipe 12. The gas is then expanded invalve 20 and partially liquefied. The liquefied gas is stored in 14. Theliquid can be removed by valve 15, and the non-liquefied portlon is sentinto interchanger 11 through pipes 13 and 12 and then to interchanger 18and by heattransfer with the gas entering as through 17, is brought toroom temperature.

The interchangers 11 and 18 could be united into one. It is preferableto have two interchangers, which gives one the advantage of limiting thecondensationof moisture and also of frost to practically interchanger 18and the necessary defrosting can be done without disturbing interchanger11. The means for heating the interchanger for defrosting are not shownin the drawing. Valve 21 may be used to drain moisture out ofinterchanger 18.

In this process, where a current of air is compressed then refrigeratedb ammonia or ither vapors of easily liquefiabih gases and is expanded inan engine doing external work, the result from the point of view ofproduction of liquid air is small but the heat content is by this meansvcry much lowered in the order of kilocalories per kilogram. Therefrigerated air is used as a refrigerant on another current of aircapable of absorbing this cold by heat transfer contact.

The air to be liquefied passes through the inter-changers 18 and 11.Before it is expanded it is quite warm relative to the cold vapors inpipe line 12. This permits of good heat transfer. If one utilizes bothcircuits of the air at 200 atmospheres, for example, in the proportionof 1 kilogram of air of the circuit cooled by the cold non-liquefiedpor- 5 tions of the air to 1.33 kilogram of the circuit cooled byammonia or the like, the result will be that instead of getting about 8calories in the form of liquid air per kilogram of air compressed byusing the first circuit above (i. e. the liquefaction circuit alone),this process has a value of the order of 30 calories per kilogram of aircompressed of the combined circuits. These quantities are not absolutebut can vary largely according to the dimensions of the installation andthe nature of the insulation and other conditions. The energy necessaryfor the production of cold by ammonia is very small in comparison withthe energy necessary for the total compression of the air, the resultbeing that one not only produces an unusual quantity of liquid air perkilogram of air treated, but also the energy to produce a kilo ram ofliquid air is very much reduced relative to the present ractice.

T e process is not limited to the means of realizing same described butcan be varied considerably.

The circuit for refrigerating is not limited to air even when air is tobe liquefied but other ases could be used as nitrogen or hydrogen.

f the gas used in the circuit for refrigerating is to be recuperated andis not the same as the gas to be liquefied, an additional interchangeror an additional set of tubes in interehangers 11 and 18 and thenecessary piping changes (which are not shown in the drawing) will haveto be provided to avoid contamination between the gas in therefrigerating circuit and the vapors of the gas that is liquefied. Thecircuits need not be at the same pressure but the pressure and volumesshould be chosen in such a manner as to obtain the necessary heattransfer and to bring the cold vapors to room temperature.

I claim:

1. An apparatus for liquefying a gas comprising means for compressing aportion of the gas, means for compressing, cooling and expandin arefrigerant, means to bring the contact with the compressed gas wherebythe cold expanded refrigerant into heat transfer gas will be cooled andthe refrigerant will be sated to room temperature, means to expend thecooled gas in an expansion valve and/or expansion engine producingexternal work, means to employ the cooled gas as a refrigerant to coolby heat transfer contact an other portion of compressed gas whereby therefrigerant will be heated to room temperature and the compressed gaswill be cooled, means to expand and partially liquefy the 2. Anapparatus for liquefying a gas com- 65 prising means for compressing aportionl of the gas, means for compressing, cooling and expanding arefrigerant, means to bring the cold expanded refrigerant into heattransfer contact with the compressed gas whereby the gas will be cooledand the refrigerant will be heated to room temperature, means to expandand partially liquefy the cooled gas in an expansion valve and/orexpansion engine producing external work, means to employ thenon-liquefied portion of the gas as a refugerant to cool by heattransfer contact another portion of compressed gas whereby therefrigerant will be heated to room temperature and the compressed gaswill be cooled, means to expand and partially liquefy the gas.

3. A process of liquefying gas, comprising compressing one portion ofgas, compressing a. second portion of gas, cooling said second portionby a refrigerant which is more easily liqueliable than the gas which isto be liquefied, expanding said second portion with a production of alower temperature, and using the cold expanded second portion to coolthe first portion.

4. A process of liquefying gas, comprising compressing one portion ofgas, com ressing a second portion of gas, cooling sai second portion bya refrigerant which is more easily liqueliable than the gas which is tobe liquefied, expanding said second portion with a productlon of a lowertemperature, using the cold expanded second portion to cool the firstportion, expanding and partially liquefyin said cold first portion, andusing the noniquefied part of said first portion after expansion forcooling only the first of said portions before the first portion isexpanded.

5. A process of liquefying gas, comprising compressing one portion ofgas, com I'essing a second portion of gas, cooling sai second portion byan external refrigerant, expandm said second portion with a productionof a ower temperature, and using the cold expanded second portion tocool the first portion.

6. A process of liquefying gas, comprising compressing one portion ofas, com ressin a second portion of s, coo ing sai secon portion by anexterna refrigerant, expanding said second portion with a production ofa lower temperature, expanding and partially liquefymg said cold firstportion. and using the non-liquefied part of said first ortion after exansion for cooling only the rst of said portions before the firstportion is expanded.

7. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bynon-regenerative cooling means, expanding said second portion with aproduction of a lower temperature, and using the cold expanded secondportion to cool the first portion.

8. A process of liquefying gas, campusing compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bynonregenerative cooling means, expanding said second portion with aproduction of a lower temperature, expanding and partially liquefyinsaid cold first portion, and using the non-liquefied part of said firstortion after expansion for cooling only the rst of said portions beforethe first portion is expanded.

9. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liqu'efiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, and cooling said first portion by heat exchange with saidcold expanded second portion.

10. A procefs of liquefying gas, compris ing compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, and cooling said first portion by countercurrent heatexchange with said cold expanded second portion.

11. A process of liquefying gas, comprising compressing one portion ofgas, comressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, and cooling said first portion by heat exchange with saidcold expanded second portion in such manner that the second portion isbrought to substantially the temperature of the entering first portion.

12. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, and cooling said first portion by heat exchange with saidcold expanded secondportion while said first portion is at substantiallyroom temperature.

13. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, and cooling said first portion by heat exchange with saidcold expanded second portion while said first portion is at asubstantially higher temperature than the temperature of the cooledexpanded second portion before heat exchange.

14. A process of liquefyin gas, comprising compressing one portion 0gas, compressing a second portion of gas, cooling said second portion byan external refrigerant, expanding said second portion with a productionof a lower temperature, cooling said first portion by a countercurrentheat exchange with said cold expanded second portion in such manner thatthe temperature of the first portion is reduced and the second portionis discharged at substantially the temperature of the entering firstportion.

15. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion byan external refrigerant, ex paneling said second portion with aproduction of a lower temperature, cooling said first portion by acountercurrent heat exchange with said cold expanded second portion insuch manner that the temperature of the first portion is reduced tosubstantially that of the expanded second portion and the second portionis discharged at substantially the temperature of the entering firstportion.

16. A process of liqucfying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, cooling said first portion by a countercurrent heatexchange with said cold expanded second portion in such manner that thetemperature of the first portion is reduced and the second portion isdischarged at substantially the temperature of the entering firstportion.

17. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, cooling said first portion by a countercurrent heatexchange with said cold expanded second portion in such manner that thetemperature of the first portion is reduced to substantially that of theexpanded second portion and the second portion is discharged atsubstantially the temperature of the entering first portion.

18. A process of liquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion bya refrigerant which is more easily liquefiable than the gas which is tobe liquefied, expanding said second portion with a production of a lowertemperature, cooling said first portion by a countercurrent heatexchange with said cold expanded second portion in such manner that thetemperature of the first portion is reduced to substantially that of theexpanded second portion at the discharge end and the second portion isdischarged at the other end at substantially the temperature of theentering first portion.

19. A process of liquefyin gas, comprisingcompressingone p0 ionogas,compressing a second portion 0 gas, cooling said second portion bv arefrigerant which is more easily liquefiable than the gas which is to beliquefied, expanding said second portion with a production of a lowertemperature, cooling said first portion by heat exchange with said coldexpanded second portion, ex-

pending and partially liquefying said cold first portion and using thenon-1i uefied part of said first ortion after expansion for cooling onlythe rst of said ortions before the first portion is expander.

20. A process of Iiquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion byan external refrigerant, expanding said second portion with a productionof a lower temperature, cooling said first portion by a countercurrentheat exchange with said cold expanded second portion in such manner thatthe temperature of the first portion is reduced to substantially that ofthe expanded second portion and the second portion is discharged atsubstantially the temperature of the entering first portion, expandingand partially liquefying said cold first portion, and using thenon-liquefied part of the first portion after expansion for cooling onlythe rst of said portions before it is expan ed.

In testimony whereof I aifix my si ature.

ISAAC H. L VIN.

CERTIFICATE OF CORRECTION.

Patent No. I, 892. 155.

December 27, I932.

ISAAC I'I. LEVIN.

it is hereby certified that error appears above numbered patentrequiring correction as l, strike out the words "cold expandedrefrigerant into sort the same to follow "the" in line 50; should beread with this correction therein record of the case in the PatentOffice.

in the printed specification of the Page 2, line 52. claim follows:

heat transfer" and inand that the said Letters Patent that the same mayconform to the Signed and sealed this 21st day of February, A. D. 1933.

(Seal) M. 1.. Moore, Acting Commissioner of Patents.

charged at the other end at substantially the temperature of theentering first portion.

19. A process of liquefyin gas, comprisingcompressingone p0 ionogas,compressing a second portion 0 gas, cooling said second portion bv arefrigerant which is more easily liquefiable than the gas which is to beliquefied, expanding said second portion with a production of a lowertemperature, cooling said first portion by heat exchange with said coldexpanded second portion, ex-

pending and partially liquefying said cold first portion and using thenon-1i uefied part of said first ortion after expansion for cooling onlythe rst of said ortions before the first portion is expander.

20. A process of Iiquefying gas, comprising compressing one portion ofgas, compressing a second portion of gas, cooling said second portion byan external refrigerant, expanding said second portion with a productionof a lower temperature, cooling said first portion by a countercurrentheat exchange with said cold expanded second portion in such manner thatthe temperature of the first portion is reduced to substantially that ofthe expanded second portion and the second portion is discharged atsubstantially the temperature of the entering first portion, expandingand partially liquefying said cold first portion, and using thenon-liquefied part of the first portion after expansion for cooling onlythe rst of said portions before it is expan ed.

In testimony whereof I aifix my si ature.

ISAAC H. L VIN.

CERTIFICATE OF CORRECTION.

Patent No. I, 892. 155.

December 27, I932.

ISAAC I'I. LEVIN.

it is hereby certified that error appears above numbered patentrequiring correction as l, strike out the words "cold expandedrefrigerant into sort the same to follow "the" in line 50; should beread with this correction therein record of the case in the PatentOffice.

in the printed specification of the Page 2, line 52. claim follows:

heat transfer" and inand that the said Letters Patent that the same mayconform to the Signed and sealed this 21st day of February, A. D. 1933.

(Seal) M. 1.. Moore, Acting Commissioner of Patents.

